Package Substrate and Method for Forming the Same

ABSTRACT

A package substrate is disclosed. The package substrate includes a substrate body having a conductive portion, a plurality of insulation portions and two surfaces opposing to each other; and a plurality of bonding layers for heat dissipation formed on the two surfaces of the substrate body, conducted via the conductive portion and separated from one another by the insulation portions. A method for forming the package substrate is also disclosed.

FIELD OF INVENTION

The present invention relates to a package substrate and a method forforming the package substrate, and more particularly, to a packagesubstrate for increasing heat dissipation and a method for forming thepackage substrate.

BACKGROUND OF THE INVENTION

In the development trend of electronic industry, electronic products getthinner and lighter with high performance, function and speed. Inaddition, it is a trend to enhance heat dissipation to meet requirementof electronic devices with long life.

A conventional package substrate for attaching a light emitting diode(LED) 14 is shown in FIG. 1A and FIG. 1B. A ceramic substrate 10 havinga surface 10 a and a surface 10 b, a bonding layer 13 is formed on thesurfaces 10 a and 10 b of the ceramic substrate 10, and conductive holes100 are formed through the ceramic substrate 10 for electricallyconnecting the bonding layer 13 on the surfaces 10 a and 10 b of theceramic substrate 10. A light emitting diode 14 is mounted on thebonding layer 13 on the surface 10 a of the ceramic substrate 10.

As shown in FIG. 1A, the P electrode and the N electrode of the LED 14are disposed on the same surface of the LED 14, such that the Pelectrode and the N electrode of the LED 14 are connected to the bondinglayer 13 via wirings 15. Alternatively, as shown in FIG. 1B, the Pelectrode and the N electrode of the LED 14′ are disposed on differentsurfaces of the LED 14′, and thus one electrode is connected to thebonding layer 13 via a wiring 15, and the other electrode is directlyand electrically connected to the bonding layer 13.

Heat generates during the operation of the LED 14, 14′, and the heat isintroduced to the surface 10 b of the ceramic substrate 10 viaconductive holes 100. In addition, the material of the ceramic substrate10 also facilitates heat dissipation.

However, the conventional ceramic substrate 10 has the coefficient ofthermal conductivity as 17-170 w/m.k, which is significantly smallerthan that (250 w/m.k) of aluminum material and also smaller than that(400 w/m.k) of copper material. The ceramic substrate 10 has worsethermal conductivity and heat dissipation than metal material. Thebonding layer 13 and the conductive holes 100 facilitate heatdissipation, but the volume of the conductive holes 100 is much smallerthan that of the ceramic substrate 10. Therefore, the heat dissipationefficiency of the ceramic substrate 10 is not compatible with metalmaterials.

Accordingly, there is an urgent need to enhance the effect of heatdissipation in the art.

SUMMARY OF THE INVENTION

The present invention provides a package substrate, including asubstrate body having a conductive portion, an insulation portion, andtwo surfaces opposing to each other; and a plurality of bonding layersformed on the two surfaces of the substrate body, conducted via theconductive portion for heat dissipation, and separated from one anotherby the insulation portion.

In the package substrate of the present invention, the conductiveportion is made of metal material, and the insulation portion is made ofpolymer or ceramics.

Further, the insulation portions of the present invention may bearranged alternately for dividing the substrate body into a plurality ofregions.

In addition, the bonding layer may have a pad for attaching a lightemitting diode.

The present invention provides a method for forming a package substrate,including the steps of: providing a metal plate having a first surfaceand a second surface opposing to the first surface; forming a pluralityof trenches on the first surface of the metal plate; providinginsulation material in the trenches; removing metal plate material underthe second surface of the metal plate, and exposing the insulationmaterial in the trenches from the first and second surfaces of thesubstrate body to form a substrate body having two surfaces opposing toeach other, wherein the substrate body includes a conductive portionmade of the metal plate, and an insulation portion made of theinsulation material; and forming a plurality of bonding layers on thetwo surfaces of the substrate body, wherein the bonding layers areconducted via the conductive portion for heat dissipation, and separatedfrom one another by the insulation portion.

In the method of the present invention, the trenches are arrangedalternately for dividing the first surface of the metal plate into aplurality of regions.

The method of the present invention further includes the steps offorming the insulation material on the first surface of the metal plateand in the trenches; and removing a portion of the insulation materialon the first surface of the metal plate and remaining the insulationmaterial in the trenches.

The present invention further provides a method for forming a packagesubstrate, including the steps of: providing an insulation plate;forming a plurality hollow regions through the insulation plate;providing metal material in the hollow regions to form a substrate bodywith two surfaces opposing to each other, wherein the substrate bodyincludes a conductive portion made of the metal material, and aninsulation portion made of the insulation plate with hollow regions; andforming a plurality of bonding layers on the two surfaces of thesubstrate body, wherein the bonding layers are conducted via theconductive portion for heat dissipation, and separated from one anotherby the insulation portion.

In the method of present invention, the hollow regions are arrangedalternately to form a plurality of isolated regions.

In the method of the present invention, the metal plate or the metalmaterial is copper (Cu) or aluminum (Al).

In the method of the present invention, the insulation portion is madeof polymer or ceramics.

In addition, in the method of the present invention, the bonding layermay have a pad for attaching a light emitting diode.

In the present invention, the substrate body includes a conductiveportion and an insulation portion, and there is a significant ratio ofthe volume of the conductive portion to the volume of the insulationportion. The volume of the conductive holes in the conventional ceramicplate is extremely small. In contrast, the heat dissipation effect ofthe substrate body in the present invention is significantly increasedto prevent the bonding layer from burn out owing to overheating and toenhance heat dissipation of a light emitting diode.

Moreover, the conductive holes are used as conductive paths in the priorart. In contrast, the conductive portion is the conductive path for theupper and lower bonding layers in the present invention to increaseelectrical conductivity, and the insulation portion of the presentinvention prevents the bonding layers from a short circuit.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B (PRIOR ART) are respectively a cross-sectional schematicview of a light emitting diode (LED) mounted on a package substrateaccording to different embodiments of the prior art;

FIGS. 2A to 2E are cross-sectional views showing a method forfabricating a package substrate according to an embodiment of thepresent invention, wherein FIG. 2A′ is a top view of a metal plate;

FIGS. 2F and 2F′ are respectively a cross-sectional schematic view of anLED mounted on a package substrate according to different embodiments ofthe present invention;

FIGS. 3A to 3C are schematic cross-sectional diagrams showing a processof a substrate body of a package substrate according to anotherembodiment of the present invention, wherein FIG. 3B′ is a top view ofan insulation plate; and

FIG. 4 is a top view of another insulation plate in the process of FIGS.3A to 3C, wherein FIG. 4′ is a partially enlarged view of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following specific examples are used for illustrating the presentinvention. A person skilled in the art can easily conceive the otheradvantages and effects of the present invention.

According to the embodiments shown in FIG. 2A to FIG. 2F and FIG. 2A′,the terms “above” and “under” are used for illustrating relativedirection of the features rather than limiting the scope of the presentinvention.

FIG. 2A to FIG. 2E show the method for forming a package substrate ofthe present invention.

As shown in FIG. 2A and FIG. 2A′, a metal plate 20 having a firstsurface 20 a and a second surface 20 b opposing to the first surface 20a is provided. The metal plate 20 is made of a thermal conductivematerial such as copper (Cu) or aluminum (Al). A plurality of trenches200 are formed on the first surface 20 a of the metal plate 20, and thetrenches 200 are arranged alternately in high density for dividing thefirst surface 20 a of the metal plate 20 into a plurality of regions asshown in FIG. 2A′.

As shown in FIG. 2B, an insulation material 21 is formed on the firstsurface 20 a of the metal plate 20 and in the trenches 200. Theinsulation material may be polymer such as an epoxy resin, or a ceramicmaterial such as Al₂O₃ or AlN.

As shown in FIG. 2C, the insulation material 21 on the first surface 20a of the metal plate 20 is removed, and only the insulation material 21in the trenches is remained.

As shown in FIG. 2D, the portion of the metal plate 20 under the secondsurface 20 b of the metal plate 20 is removed, and the remaining metalplate 20 is a conductive portion 221 to form a substrate body 22 havingan upper surface 22 a and a lower surface 22 b. The insulation material21 in the trenches 200 is exposed from the two surfaces 22 a, 22 b ofthe substrate body 22 to form an insulation portion 220. The volume ofthe conductive portion 221 is larger than the volume of the insulationportion 220.

As shown in FIG. 2E, bonding layers 23 a, 23 b are formed on the uppersurface 22 a and the lower surface 22 b of the substrate body 22, andconducted via the conductive portion 221. The bonding layers 23 a, 23 bare separated by the insulation portions 220 to effectively prevent thebonding layers 23 a, 23 b from a short circuit.

FIG. 2F and FIG. 2F′ show an embodiment using the above packagesubstrate. As shown in FIG. 2F, the bonding layer 23 a on the surface 22a of the substrate body 22 has electrical connection pads 230 and a pad231. In the following process, the P electrode and the N electrode aredisposed on the same surface of a light emitting diode (LED) 24, whichis attached on the pad 231. The P and N electrodes of the light emittingdiode 24 are electrically connected to the electrical connection pad 230by the wiring 25, and the heat dissipation of the LED 24 is performedvia the conductive portion 221.

Alternatively, as shown in FIG. 2F′, the P electrode and the N electrodeare disposed on different surfaces, such as top surface and bottomsurface, of a light emitting diode (LED) 24′. The electrode on the topsurface of the LED 24′ is electrically connected to the electricalconnection pad 230 by the wiring 25, and the electrode on the bottomsurface of the LED 24′ is directly and electrically connected to thebonding layer 23. The heat dissipation of the LED 24′ is performed viathe conductive portion 221.

The most volume of the substrate body 22 is made of the conductiveportion 221 in the present invention. The coefficient of thermalconductivity of metal material is higher than the common material. Forexample, the coefficient of thermal conductivity of aluminum material is250 w/m.k, and the coefficient of thermal conductivity of coppermaterial is 400 w/m.k. In comparison with the conventional ceramicsubstrate, the substrate body 22 of the present invention has muchbetter thermal conductivity and heat dissipation, and thus significantlyenhances performance and extends life of the light emitting diodes 24,24′.

Further, the conductive portion 221 of the present invention is used asa conductive path for the bonding layers 23 a, 23 b on the upper andlower surfaces. Therefore, the present invention increases electricalconductivity by using only the insulation portion 220, so as to preventthe bonding layers 23 a, 23 b from a short circuit.

FIG. 3A to FIG. 3C show another embodiment of the method for forming apackage substrate in the present invention. This embodiment is similarto the above embodiment except the procedure for forming the substratebody 32. The similar procedure is not described in this embodiment.

As shown in FIG. 3A, an insulation plate 30 is provided.

As shown in FIG. 3B and FIG. 3B′, a plurality of hollow regions 300 areformed through the insulation plate 30. The volume of the hollow regionsis larger than the volume of the remaining insulation plate 30.

As shown in FIG. 3C, the metal material is formed in the hollow regions300. For example, the metal material is filled in the hollow regions 300to form a substrate body 32 having an upper surface 32 a and a lowersurface 32 b. The substrate body 32 includes a conductive portion 321made of the metal material and an insulation portion 320 through theinsulation plate 30. The volume of the conductive portion 321 is largerthan the volume of the insulation portion 320.

Referring to FIG. 4 and FIG. 4′, an insulation plate 40 has a pluralityof hollow regions 400 for receiving the metal material. A hollow region400 includes a rectangular hole 400 a and two circular holes 400 bdisposed at the same side and outside the angle of the rectangular hole400 a. The hollow regions 400 are aligned in an array. In the followingprocedure, the conductive potion in the rectangular hole 400 a is usedfor carrying a chip and providing a path for heat dissipation of thechip, and the conductive portion in the circular hole 400 b is used forelectrical connection of the bonding layers on the upper and lowersurfaces of the substrate.

As shown in FIGS. 2F and 2F′, the present invention further provides apackage substrate, including a substrate body 22 having two surfaces 22a, 22 b opposing to each other; and bonding layers 23 a, 23 brespectively formed on the surfaces 22 a, 22 b of the substrate body 22.

The substrate body 22 includes conductive portions 221 and insulationportions 220, and the volume of the conductive portions is larger thanthe volume of the insulation portions 220. The conductive portion 221 ismade of copper or aluminum for heat dissipation. The insulation portions220 are formed through the surfaces 22 a, 22 b of the substrate body 22.The insulation portions 220 are arranged alternately for dividing thesubstrate body 22 into a plurality of regions, wherein the conductiveportion 221 is formed in the region. The insulation region 220 is madeof polymer or ceramic material.

The bonding layers 23 a, 23 b are conducted via the conductive portion221, and separated by the insulation portions 220. Further, the bondinglayer 23 a has pads 231 for attaching light emitting diodes 24, 24′. Thelight emitting diodes 24, 24′ are electrically connected to the bondinglayer 23 a, and the heat dissipation of the light emitting diodes 24,24′ is performed via the conductive portion 221.

In the present invention, the volume of the conductive portion of thesubstrate body is significantly larger than that in the prior art, so asto significantly increase heat dissipation, to prevent the bonding layerfrom burn out owing to overheating and to extend life of the lightemitting diode.

In addition, the conductive portion of the substrate body is theconductive path for the upper and lower bonding layers in the presentinvention to increase electrical conductivity, and the insulationportion of the present invention prevents the bonding layers from ashort circuit.

The invention has been described using exemplary preferred embodiments.However, it is to be understood that the scope of the invention is notlimited to the disclosed arrangements. The scope of the claims,therefore, should be accorded the broadest interpretation, so as toencompass all such modifications and similar arrangements.

1. A package substrate, comprising: a substrate body having a conductiveportion, a plurality of insulation portions and two surfaces opposing toeach other; and a plurality of bonding layers for heat dissipationformed on the two surfaces of the substrate body, conducted via theconductive portion and separated from one another by the insulationportions.
 2. The package substrate of claim 1, wherein the conductiveportion is made of copper or aluminum.
 3. The package substrate of claim1, wherein the insulation portions are made of polymer or ceramics. 4.The package substrate of claim 1, wherein the insulation portions arearranged alternately for dividing the substrate body into a plurality ofregions.
 5. The package substrate of claim 1, wherein a volume of theconductive portion is larger than a volume of the insulation portion. 6.The package substrate of claim 1, wherein the bonding layer has a padfor attaching a light emitting diode.
 7. The package substrate of claim1, wherein the light emitting diode is electrically connected to thebonding layer.
 8. A method for forming a package substrate, comprisingthe steps of: providing a metal plate having a first surface and asecond surface opposing to the first surface; forming a plurality oftrenches on the first surface of the metal plate; providing insulationmaterial in the trenches; removing metal plate material under the secondsurface of the metal plate, and exposing the insulation material in thetrenches from the first and second surfaces of the substrate body toform a substrate body having two surfaces opposing to each other,wherein the substrate body includes a conductive portion made of themetal plate, and an insulation portion made of the insulation material;and forming a plurality of bonding layers on the two surfaces of thesubstrate body, wherein the bonding layers are conducted via theconductive portion for heat dissipation, and separated from one anotherby the insulation portion.
 9. The method of claim 8, wherein the metalplate is made of copper or aluminum.
 10. The method of claim 8, whereinthe trenches are arranged alternately for dividing the first surface ofthe metal plate into a plurality of regions.
 11. The method of claim 8,wherein the insulation portion is made of polymer or ceramics.
 12. Themethod of claim 8, wherein the insulation portion is formed by the stepsof: forming the insulation material on the first surface of the metalplate and in the trenches; and removing a portion of the insulationmaterial on the first surface of the metal plate and remaining theinsulation material in the trenches.
 13. The method of claim 8, whereina volume of the conductive portion is larger than a volume of theinsulation portion.
 14. The method of claim 8, wherein the bonding layerhas a pad for attaching a light emitting diode.
 15. A method for forminga package substrate, comprising the steps of: providing an insulationplate; forming a plurality hollow regions through the insulation plate;providing metal material in the hollow regions to form a substrate bodywith two surfaces opposing to each other, wherein the substrate bodyincludes a conductive portion made of the metal material, and aninsulation portion made of the insulation plate with hollow regions; andforming a plurality of bonding layers on the two surfaces of thesubstrate body, wherein the bonding layers are conducted via theconductive portion for heat dissipation, and separated from one anotherby the insulation portion.
 16. The method of claim 15, wherein the metalmaterial is copper or aluminum.
 17. The method of claim 15, wherein thehollow regions are arranged alternately to form a plurality of isolatedregions.
 18. The method of claim 15, wherein the insulation portion ismade of polymer or ceramics.
 19. The method of claim 15, wherein avolume of the conductive portion is larger than a volume of theinsulation portion.
 20. The method of claim 1, wherein the bonding layerhas a pad for attaching a light emitting diode.